Re-organize VIXL's doc/ and mention AArch32

Updates the top README to reflect changes done with the support for
AArch32. Take the opportunity to re-organize our documentation files
structure and seperate `aarch32` and `aarch64` at the top-level.

Additionally, the title now mentions this is the
development version of VIXL.

doc/
├── aarch32
│   ├── design
│   │   ├── code-generation-aarch32.md
│   │   └── literal-pool-aarch32.md
│   └── getting-started-aarch32.md
├── aarch64
│   ├── getting-started-aarch64.md
│   ├── supported-instructions-aarch64.md
│   └── topics
│       ├── extending-the-disassembler.md
│       ├── index.md
│       └── ycm.md
└── changelog.md

Change-Id: Ida9547a1de30886a112360e4b2beafa7cb0ac7b9

8 files changed, 9 insertions, 1 deletions

diff --git a/doc/design/code-generation.md b/doc/aarch32/design/code-generation-aarch32.md
index 32952b0a..32952b0a 100644
--- a/doc/design/code-generation.md
+++ b/doc/aarch32/design/code-generation-aarch32.md
diff --git a/doc/design/aarch32/literal-pool.md b/doc/aarch32/design/literal-pool-aarch32.md
index 95cc76de..95cc76de 100644
--- a/doc/design/aarch32/literal-pool.md
+++ b/doc/aarch32/design/literal-pool-aarch32.md
diff --git a/doc/getting-started-aarch32.md b/doc/aarch32/getting-started-aarch32.md
index f4fdccbe..f4fdccbe 100644
--- a/doc/getting-started-aarch32.md
+++ b/doc/aarch32/getting-started-aarch32.md
diff --git a/doc/getting-started-aarch64.md b/doc/aarch64/getting-started-aarch64.md
index 4637a8dc..ff8c2e71 100644
--- a/doc/getting-started-aarch64.md
+++ b/doc/aarch64/getting-started-aarch64.md
@@ -197,3 +197,11 @@ The example shown in this tutorial is very simple, because the goal was to
 demonstrate the basics of the VIXL framework. There are more complex code
 examples in the VIXL `examples/aarch64` directory showing more features of both the
 macro assembler and the ARMv8 architecture.
+
+
+Extras
+------
+
+In addition to this document and the [examples](/examples/aarch64), you can find
+documentation and guides on various topics that may be helpful
+[here](/doc/aarch64/topics/index.md).
diff --git a/doc/supported-instructions-aarch64.md b/doc/aarch64/supported-instructions-aarch64.md
index b9d2e626..b9d2e626 100644
--- a/doc/supported-instructions-aarch64.md
+++ b/doc/aarch64/supported-instructions-aarch64.md
diff --git a/doc/topics/aarch64/extending-the-disassembler.md b/doc/aarch64/topics/extending-the-disassembler.md
index 60b04b3f..60b04b3f 100644
--- a/doc/topics/aarch64/extending-the-disassembler.md
+++ b/doc/aarch64/topics/extending-the-disassembler.md
diff --git a/doc/topics/aarch64/index.md b/doc/aarch64/topics/index.md
index e38aaad3..0e114503 100644
--- a/doc/topics/aarch64/index.md
+++ b/doc/aarch64/topics/index.md
@@ -2,7 +2,7 @@ We will try to add documentation for topics that may be useful to VIXL users. If
 you think of any topic that may be useful and is not listed here, please contact
 us at <vixl@arm.com>.
 
-You can also have a look at the ['getting started' page](../getting-started.md).
+You can also have a look at the ['getting started' page](../getting-started-aarch64.md).
 
 * [Extending and customizing the disassembler](extending-the-disassembler.md)
 * [Using VIM YouCompleteMe with VIXL](ycm.md)
diff --git a/doc/topics/aarch64/ycm.md b/doc/aarch64/topics/ycm.md
index 36371cf3..36371cf3 100644
--- a/doc/topics/aarch64/ycm.md
+++ b/doc/aarch64/topics/ycm.md